A drug that has been used to treat leprosy for decades has also been found to be effective against Covid-19, according to a study by researchers from Hong Kong, the United States and Denmark.

The newly identified use of clofazimine meant that a more affordable and accessible treatment option could be made available in the fight against the coronavirus, which has so far infected more than 120 million people and caused over 2.6 million deaths globally.

Describing the finding as “very exciting”, University of Hong Kong infectious disease expert Professor Yuen Kwok-yung, a member of the research team, said more work would be needed to ascertain the use of the drug.

“The discovery of anti-leprosy drug clofazimine being active against Sars-CoV-2 in test tubes and hamsters is very exciting,” Yuen said.

“But this is just the first step. A randomised phase two/three clinical trial is necessary to know whether it has a place in the treatment of Covid-19.”

Scientists conducting the research believed the discovery of the new function for clofazimine, which was first used in 1969 to treat leprosy, could improve the treatment options for Covid-19.

The study, which was published in the latest issue of international scientific journal Nature, found that clofazimine could block the coronavirus from entering into cells and disrupt its genetic replication. It could also reduce the replication of other coronaviruses such as those behind the Middle East respiratory syndrome and severe acute respiratory syndrome.

Professor Yuen Kwok-yung, microbiologist from the University of Hong Kong, was part of the research team.

The drug was found to be able to suppress the viral load in the lungs of golden Syrian hamsters infected with Covid-19. It was also able to reduce lung damage and prevent cytokine storm, a severe immune reaction, that could be triggered by the coronavirus.

Shedding of the coronavirus, a possible contagious condition when the virus replicates inside a body and is released into the environment, was also reduced when nasal and faecal samples of the hamsters treated with the drug were tested.

The reduced viral load in the animal faeces was also identified in both settings when the drug was used as a preventive medication or as part of the treatment.

Researchers also found that using the anti-leprosy drug together with remdesivir, prescribed for treating seriously ill Covid-19 patients in hospital, could further boost recovery.

“Taken together, the antiviral synergy between low-dose remdesivir and clofazimine significantly improved viral control, with reduced body weight loss, suppressed pulmonary virus titre, and nasal virus shedding, as well as decreased drug dosages,” researchers wrote in the article, adding that a combination use of drugs could reduce treatment costs and extend global supplies of remdesivir.

While remdesivir has been used across the world to treat Covid-19, researchers said the complex manufacturing process meant a high treatment cost and only a few million patients could get access to it in the next two years. In contrast, clofazimine only costs US$1.43 per 100 milligrams.

“[It] can be considered as one of the potential countermeasures for global control of the Covid-19 pandemic, especially in developing countries,” the article read.

Researchers said clinical trials in evaluating the efficacy of the drug for Covid-19 should be considered to open up more treatment options.